It sounds like some companies are finding a niche making indoor map apps for convention centers, airports, malls -- basically, any big space frequented by a lot of people. I would think this is something the facilities would want to do themselves, though, since they'd be more able to keep it updated (the article does mention a mall that wants to do it on its own).
Would this be useful for events? Probably, though now that so many shows are doing their own event-specific apps that include facility guides, it might be a bit redundant. I wonder when/if these apps will make signage redundant?